Authorization bypass via path binding override in elixir-grpc/grpc HTTP transcoding (CVE-2026-48599)
Published Last modified Sources: CVE.org, Hersteller, EUVD, OSV
What is affected, what to do
Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body. In 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence.
Update Elixir-grpc Grpc to version 1.0.0.
- Affected
- Elixir-grpc Grpc
lt 0.8.0..1.0.0
- Elixir-grpc Grpc
- Fixed in
- Elixir-grpc Grpc
1.0.0
- Elixir-grpc Grpc
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
7.6
XIEM Effective CVSS
Highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v4
7.6
CVSS v4
Severity High on the scale from 0 to 10.
Source: CVE.org, Hersteller, EUVD, OSV
0.3 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 27.8
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 62.40 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.6 Methodology
CVSS v4
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.6
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.3 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 27.8
- Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
- CISA assessment (SSVC)
- Exploitation: proof of concept · not automatable · Technical impact: total
- Source: CISA Vulnrichment, as of 16 June 2026
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-639
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body. In 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence. A request such as GET /users/me/profile?user_id=victim (or a POST with {"user_id": "victim"} when body: "*") yields a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value. Any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks is silently bypassed. This issue affects grpc: from 0.8.0 before 1.0.0.
Source: NVD (NIST), GitHub Security Advisories, ENISA EUVD, cvelistv5, OSV (Open Source Vulnerabilities)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| elixir-grpc | grpc |
|
|
| hex | grpc |
|
|
Vendors and products
Weakness classes (CWE)
CWE-639Authorization Bypass Through User-Controlled Key
Base
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Entry at MITRE CWE-639
References & sources
- github.comelixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cqadvisory, Vendor advisory, related, euvd
- cna.erlef.orgEEF CNA record for CVE-2026-48599web, related, euvd
- github.comFix commit 33b6a09 in elixir-grpc/grpcfix, Patch, euvd
- hex.pmpackages/grpcpackage
- NVD (NIST)vuln/detail/CVE-2026-48599advisory
- github.comelixir-grpc/grpc/pull/541web
- github.comelixir-grpc/grpcpackage
- github.comelixir-grpc/grpc/releases/tag/v1.0.0web
- OSV (Open Source Vulnerabilities)OSV record EEF-CVE-2026-48599web, related, euvd
- github.comIntroducing commit 8aaf3d3 in elixir-grpc/grpcweb, related, euvd
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedEEF
Description added or changed
New references:- https://cna.erlef.org/cves/CVE-2026-48599.html
- https://github.com/elixir-grpc/grpc/commit/33b6a095dbc91c6dee3c7b90893d7d74952e82e4
- https://github.com/elixir-grpc/grpc/commit/8aaf3d3a8c4c7b08ac65e9c6f254e0d24da1d048
- https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cq
and 1 more reference
Show 10 original changes
Individual changes of this event as published by NVD Type Action Before After Description changed Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body. In 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence. A request such as GET /users/me/profile?user_id=victim (or a POST with {"user_id": "victim"} when body: "*") yields a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value. Any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks is silently bypassed. This issue affects grpc from 0.8.0 before 1.0.0.Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body. In 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence. A request such as GET /users/me/profile?user_id=victim (or a POST with {"user_id": "victim"} when body: "*") yields a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value. Any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks is silently bypassed. This issue affects grpc: from 0.8.0 before 1.0.0.Reference added —https://cna.erlef.org/cves/CVE-2026-48599.htmlReference added —https://github.com/elixir-grpc/grpc/commit/33b6a095dbc91c6dee3c7b90893d7d74952e82e4Reference added —https://github.com/elixir-grpc/grpc/commit/8aaf3d3a8c4c7b08ac65e9c6f254e0d24da1d048Reference added —https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cqReference added —https://osv.dev/vulnerability/EEF-CVE-2026-48599Reference removed https://cna.erlef.org/cves/CVE-2026-48599.html—Reference removed https://github.com/elixir-grpc/grpc/commit/33b6a095dbc91c6dee3c7b90893d7d74952e82e4—Reference removed https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cq—Reference removed https://osv.dev/vulnerability/EEF-CVE-2026-48599—Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Record modifiedCISA ADP
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cqReference removed https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cq—Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Record modifiedCISA ADP
Show the original change
Individual changes of this event as published by NVD Type Action Before After Reference added —https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cqSource identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
ReceivedEEF
CVSS V4.0: AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness type: CWE-639
Description added or changed
Show 7 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body. In 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence. A request such as GET /users/me/profile?user_id=victim (or a POST with {"user_id": "victim"} when body: "*") yields a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value. Any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks is silently bypassed. This issue affects grpc from 0.8.0 before 1.0.0.CVSS added —AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XWeakness type (CWE) added —CWE-639Reference added —https://cna.erlef.org/cves/CVE-2026-48599.htmlReference added —https://github.com/elixir-grpc/grpc/commit/33b6a095dbc91c6dee3c7b90893d7d74952e82e4Reference added —https://github.com/elixir-grpc/grpc/security/advisories/GHSA-mwr4-5g34-j5cqReference added —https://osv.dev/vulnerability/EEF-CVE-2026-48599Source identifier: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
One NVD translation into another language is hidden.
Embed badge
Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.
<a href="https://intel.neosec.eu/en/cve/CVE-2026-48599"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-48599.svg?lang=en" alt="CVE-2026-48599 – NEOSEC Intel" height="20"></a>